I had an f650, in fact it was my first bike when re entering riding after too many years. It was a very nice bike, though not all that off road worthy. The newer GS model is indeed more capable.
That said, I have gone through five different dual sport bikes over the last 10 years. 250's, a 350, and a couple of 650's, air cooled and liquid cooled. Zooks and Kawis. The BMW's are harder to do do routine maintenance on and much more expensive to repair and replace busted parts. The f650was just too nice to take back into the bush. Road riding...just fine
For off road riding, the smaller displacement bikes were the easiest to pick up and more fun when beating around the back country. The 650's were a lot more work but are more comfortable for longer "Adventure" touring.. The Kawi Super Sherpa had the lowest seat of the bunch and it was easy to flat foot it with my 30" inseam. The others were some taller, A KLR 650 can be lowered a good bit by changing links and seat. A DR650 is built to be lowered at the riders need (almost both feet down).
You learn to "slip a cheek" to put a foot down when stopped. The DS bikes are taller in order to yield the needed clearance.
My favorite bike of the bunch was the Suzuki DR650. A nice used one would cost you half what the BMW would and you would have plenty of traveling money after putting some accessories on it. A new , left over would save you more than a couple of grand.
Just my two cents worth.